1. Field of the Invention
The present invention relates to a vehicular lamp.
2. Background Art
An HID lamp (High Intensity Discharge lamp), a halogen lamp, an LED (Light Emitting Diode), and the like are used as a light source of the vehicular lamp (such as a headlamp). In an optical system of a projection-type vehicular lamp, light emitted from the light source is reflected by a reflector, the light passes through a shade so as to form a cut-off line, and an object ahead a vehicle is irradiated with the light transmitted through a projector lens. In any light source, the light transmitted through the projector lens generates color separation derived from color aberration of the projector lens near an edge of a light distribution pattern. This is a common problem irrespective of a type of the light source.
A white LED that is of the light source has a strong spectrum in a specific wavelength region like an LED (a blue LED and a yellow fluorescent material are used) having a strong spectral distribution in blue and yellow and an LED (an ultraviolet LED and blue, green, and red fluorescent materials are used, or the blue LED and the red and green fluorescent materials are used) having the strong spectral distribution in blue, green, and red. Accordingly, the color separation is prominently and easily exerted when the white LED is used as the light source of the vehicular lamp.
Regardless of whether the light source has the strong spectral distribution in the specific wavelength region, unfortunately the color separation is generated in a direction in which the red is further strengthened in the light source whose correlated color temperature is low (reddish), or the color separation is generated in a direction in which the blue is further strengthened in the light source whose correlated color temperature is high (bluish).
In order to improve the problem with the color separation, for example, there is proposed a method for texturing a lens surface (see Japanese Patent Application Laid-Open (JP-A) No. 8-17045). In the method disclosed in JP-A No. 8-17045, because a luminous intensity pattern is smudged by utilizing a light scattering effect of the texturing performed to the whole of the lens surface, unfortunately deterioration of transmittance cannot be avoided and a lens characteristic is easily fluctuated according to a feature of the texturing.